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<br /> #11 Although the static stability analysis of the filtered tailings facility indicated an acceptable factor of safety,all
<br /> geotechnical input parameters were assumed without justification.The tailings densities were based on
<br /> measurements on tailings samples from a different ore deposit(Windy Gulch),an assumed ability to compact
<br /> the tailings to 95%of the maximum density within the structural zone,and an apparent confusion between dry
<br /> and moist unit weights.There was no mention of the assumed height of the water table or any discussion of the
<br /> water table height that would result in dam instability or the circumstances under which such a water table
<br /> height would occur.
<br /> #12 The diversion channels for the filtered tailings facility would be designed to accommodate a 24-hour storm
<br /> with a return period of 10 years during mine operation.On that basis,the probability of rewetting the tailings by
<br /> runoff would be 10%in any given year of mine operation and 41%over the five years of mine operation.
<br /> Following mine closure,the diversion channels would be reconstructed to accommodate a 24-hour storm with a
<br /> return period of 100 years,so that the probability of rewetting the tailings by runoff would be 1%in any given
<br /> year of the indefinite period of mine closure.There is no analysis of the consequences of rewetting either in
<br /> terms of dam stability or increasing the susceptibility of the tailings to liquefaction.
<br /> The design of the channels to accommodate a 24-hour storm with a return period of 100 years after mine
<br /> closure means that, in any given year of the indefinite time period following mine closure,the probability of
<br /> overtopping of the channels will be 1%. On that basis,the probability that overtopping of the channels will occur
<br /> at least once during,say,the next 60 years(two human generations),is 45%,so that overtopping of the
<br /> channels will essentially be an expected event for the grandchildren of the current residents of Canon City.
<br /> As before,the available documents include no discussion of the consequences of overtopping of the diversion
<br /> channels, including possible impacts on the stability of the filtered tailings facility or the possibility of liquefaction
<br /> of the lightly compacted tailings. In summary,the proposed water management infrastructure for the filtered
<br /> tailings facility is entirely inadequate.
<br /> ...the method of upstream construction is the most dangerous because, if the underlying tailings undergo
<br /> liquefaction,the dam will simply fall backwards and downwards into the liquefied tailings,even if the dam itself
<br /> does not liquefy.(P42)
<br /> The filtered tailings facility crest would be 6495 feet,6523 feet,and 6541 feet after one,three,and five years of
<br /> operation, respectively(see Figs. 11-12). Based on a minimum elevation of 6420 feet for the filtered tailings
<br /> facility...,the tailings dam heights would be 75 feet, 103 feet, 121 feet,and 153 feet for the one-year,three-
<br /> year,five-year,and ultimate configurations,respectively....
<br /> Although the water balance diagram...shows a"Water Treatment Plant"before"Treated Water to Discharge,"
<br /> the available documents do not include any plan for a water treatment plant, including no discussion of the
<br /> contaminants that would need to be removed or how they would be removed. (P37)
<br /> In other words,the main body of the application(Environmental Alternatives,2021 a)states categorically that no
<br /> water treatment will be needed,while the appendices(Environmental Alternatives,2021 b)see the need for
<br /> water treatment as a later decision to be decided based upon the results of water quality monitoring. (P38)
<br /> ---end of Dr, Emerman's comments---
<br /> Our water pollution summary and conclusion:
<br /> Zephyr plans to use a very high-risk method of upstream construction for the filtered tailings. Heavy rains
<br /> (similar to July 23,2018)could cause liquefaction of the tailings stack and release chemically treated tailings
<br /> into Grape Creek and then the Arkansas River.Where is the water treatment plant?Since tailings densities
<br /> were based on measurements on tailings samples from a different ore deposit(Windy Gulch),the application's
<br /> conclusions are not valid.
<br /> It makes no sense that any government agency would be OK with this risk given the need for consumable water
<br /> and the absence of any need for gold.
<br /> RECREATION:
<br /> Fremont County prides itself on its efforts to change the area's reputation from"mining and prisons"to a tourism
<br /> and recreation center.Over the past 10+years,the County,City,and other entities(e.g. Fremont Adventure
<br /> Recreation[FAR], Bureau of Land Management[BLM])have worked very hard and invested funds toward this
<br /> goal.
<br /> The potential mining operation puts our recreation opportunities along the Grape Creek and Arkansas River
<br /> corridors at risk.The Grape Creek area is a favorite spot for outdoor activity, including hiking,cycling,and
<br /> equestrian trails,as well as fishing. Local people and others who travel a considerable distance cherish the
<br /> quiet,scenic,natural landscape and the pristine features of the area. It is not uncommon to meet people who
<br /> have traveled to Ecology Park from Boulder(a solid three hour drive), Denver,Colorado Springs, Pueblo and
<br /> even the western slope just to be here.The hiking and bicycling trails in the area are beginning to receive
<br /> national recognition.
<br /> Grape Creek is well known for providing local anglers and tourists with opportunities to catch healthy rainbow
<br /> and brown trout.The wilderness character brings return tourism and long-term economic stability for outfitters
<br /> and businesses. Mining operation noise would severely affect the joy of fishing in the Grape Creek area and
<br /> would have a negative economic impact.
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